International publication No. WO 2013/0113330 A2 discloses a liquid formulation that includes compatible components, which are a preform for regular packaging containers.
The liquid formulation includes a carrier that is compatible with polyester and tungsten oxide (WOx) particles dispersed in the carrier. The carrier may be composed of ethylene glycol, vegetable oil, or mineral oil. The formula for the WOx particles is WO2.72. Less than 5 wt. % of the WOx particles have a particle size of more than 100 μm. In the embodiments of WO 2013/0113330 A2, the WOx particles are milled to WO2.72 particles with mean and median particle sizes of 1.22 μm and 0.97 μm (i.e., 970 nm), respectively.
The preform of a packaging container has a polymer composition, which includes polyethylene terephthalate (PET) and 12 ppm to 50 ppm of WOx particles. The polymer composition is made from the liquid formulation and components of polyethylene terephthalate (PET), which is subjected to esterification and polycondensation reactions. WO 2013/0113330 A2 did not discuss whether the polymer composition involves chemical activity or has adverse effect caused by the interactions of the liquid formulation, and the compliance of the components with food contact safety for humans.
Packaging containers, such as beverage bottles, are generally prepared from the preform through reheat blow molding. A heat lamp, such as a quartz infrared lamp, reheats the preform. To maximize energy absorption from the lamp and to increase the reheat rate of the preform, the WO2.72 particles capable of increasing infrared energy absorption are added to the polymer composition. This process increases the productivity of the packaging container. However, the food contact safety of the packaging container is not discussed in WO 2013/0113330 A2. The haze and transmittance of the preform for the packaging container of WO 2013/0113330 A2 should be developed, and the infrared energy absorption efficiency of the WOx particles used therein should be enhanced in addition to the uncertainty of food contact safety.